In this article, I'll give you an overview of the different sections of a song, and the purpose each one of them serves.

VerseMost songs start with the verse, so is the first thing the audience hears. Because of this, it is hyper-important that it’s not boring. There is nothing worse than a mopey verse sung over a lifeless instrumental. I will swipe left in 10 seconds if I hear a boring verse, and so will the rest of the world.
Here are two things you can do to keep your audience’s attention until the chorus hits:
1. The “Head Bop” approach: make it rhythmically exciting/driving2. The “Say What?!” approach: make the lyric super interesting or heavy

Pre-chorus
Not every song needs a pre-chorus (and sometimes people mistake a long verse for a pre-chorus). Really, the only reason a pre-chorus exists is to set up the chorus in the best way possible. Usually in a melodic way.
1. Melodic contrast
If the verse is high-ish in range, then the pre-chorus needs to go low so the chorus hits harder when it comes in high again. If you take out the pre-chorus, the chorus wouldn’t be as epic.
2. Melodic bridge
If the chorus hits super high and the verses are super low, the pre-chorus could act as rise up all the way to the chorus. In this example, it also kind of feels like an “EDM build.” Essentially, it makes it less of an awkward jump up.
ChorusEveryone knows what a chorus is. It’s the part that you remember when someone asks you, “How does that song go again?” Or it's the part that you sing along to at a concert. In both cases, you will need to remember it, and you need to sing it. In other words, choruses need to be simple and sing-along-able. If your audience is running out of breath, or can’t remember the melody after hearing it a few times, you’re screwed.
Here are a couple of examples of super-simple choruses. Simplicity in this case means, "repeat the lyric and melody."

Post-chorusThe post-chorus, as a section, kind of creeped into the popular conscience in the last 10 years. The way people are using it is to just pound the title in more and more and more. No extra information, no story, no nothing. Just repeat the title till you die.
Remember, the post-chorus happens after the chorus (hence the name).
BridgeHonestly, I try to avoid writing bridges as much as I can. Their only purpose is to make sure you don’t get bored halfway between the second and third chorus. (A better way to get the same result is to not write boring choruses, but whatever.)
Writing bridges is easy musically, because you can literally do whatever you want. Lyrically, though, if you do your job right, you’re gonna be fighting for things to say that aren’t redundant. My only advice: keep ‘em short.
Final Thoughts:This was a lot of information, I realize that. Fortunately, most of ya’ll already kind of know this stuff. Still, it’s good to be reminded of the function of each of these sections so that in my upcoming articles, we don’t get confused on the terminology.

Just keep in mind, the reason I talk about these sections in a slightly mechanical and unartistic way is because they’ve been specifically created to be used like this. Each section has a function in order to get the best result, which is: make the chorus the most effective it can be.
Now that we have this first building block set up, next week we can get a little more in depth! Stay tuned.

Benjamin Samama taught songwriting at Berklee College of Music from 2013–2015 and currently writes and produces pop music full-time in Los Angeles. His songs have been released by dozens of artists all over the world and enjoyed by millions.